This kind of adaptor for attaching a mobile terminal has conventionally been available (such as in PTL 1 and PTL 2). A conventional adaptor according to PTL 1, referred as a “connector”, comprises a base portion on the side of a camera-equipped mobile phone and a magnification unit on the side of a microscope, wherein the magnification unit can be attached to the base portion by turning. According to the conventional connector of PTL 1, a camera-equipped mobile phone is attached to the base portion detachably, and then the magnification unit is attached to the base portion by turning and the magnification unit is attached to a barrel of a microscope detachably. The conventional connector according to PTL 1 is thus used by connecting a camera-equipped mobile phone and a microscope via the base portion and the magnification unit.
The conventional adaptor according to PTL 2, referred as a “joining adaptor”, comprises a main body as well as a mobile terminal attaching part and an optical instrument attaching part that are provided back to back on the main body. According to the conventional adaptor in PTL 2, a mobile terminal equipped with a camera function can be attached to the main body via the mobile terminal attaching part, while an optical instrument can be attached to the main body via the optical instrument attaching part. The conventional adaptor according to PTL 2 is thus used by joining the mobile terminal equipped with the camera function and the optical instrument via the main body, the mobile terminal attaching part and the optical instrument attaching part.